Field
The present application relates to an electromagnetic actuator for a surgical or medical instrument, wherein the actuator comprises a stator and a movable element, which is at least partly composed of a paramagnetic and/or ferromagnetic material and which can be reversibly moved from a first position to a second position by the application of a switchable magnetic field, wherein the stator and the movable element have annular distal and proximal pole shoes that correspond to each other, wherein the distal pole shoes and/or the proximal pole shoes of the stator and the movable element are aligned with each other in an overlapping manner in the first position and/or in the second position. The application further relates to a surgical or medical instrument having a corresponding actuator.
Prior Art
From the document DE 10 2011 006 814 A1, an electromagnetic actuator for a surgical or medical instrument is known, wherein the actuator has a stator and a movable element, which is at least partially comprised of a paramagnetic or ferromagnetic material and can be moved from a first position into a second position by applying an electromagnetic field. Here, the movable element is held in the first or the second position by a permanent magnetic field.
The concept disclosed in document DE 10 2011 006 814 A1 for an electromagnetic actuator is used in order to move an optical component axially to the optical axis, wherein the optical component is located in the traveller. Thus, it is possible to change, for example, a focus or an enlargement of the optical system, or to change a viewing direction.
Due to repeated translatory movement or external influences such as vibrations or assembly forces, it is possible that the optical system is no longer in optimal focus. This can occur after the installation or after multiple actuations of the actuator, for instance due to manufacturing defects in the components or also positioning and alignment errors during the assembly, wherein a rotational movement of the traveller can occur. These errors are compensated by compensation procedures such as focusing and meniscus placement during the assembly, however the optical system is optimized only in one state. If subsequent changes to the optical system occur, this can negatively influence the reproduced image quality.
A further effect is that with a bistable actuator, the stroke of the actuator is set between two surfaces oriented orthogonally to the optical axis, for example stop surfaces or traveller surfaces, and these can deviate from their orthogonality to the optical axis due to manufacturing and assembly inaccuracies. This can lead to the fact that the actual stroke can be larger or smaller than intended due to the deviations, and in the case of a freely rotatable traveller can even vary.
Still further with such actuators, the setting of the stroke distance with the assembly is very complex.